Biphasic history

Industrial Chemicals Co. on biphasic catalysis can be found in a 1962 edition of the Journal of the American Chemical Society describing hydrogenations with [Co(CN)5H]3 under aqueous-organic conditions.161 Although we are not yet aware of any publication prior to that, it is highly likely that biphasic catalysis has a longer history than thought until recently. Yet, it was the systematic studies of Joo and Manassen that really laid the foundations to the field. 

Aqueous homogeneous catalysts depend on the development of polar, and thus water-soluble, ligands and their incorporation into organometallic complexes. Therefore, the history of biphasic homogeneous catalysis begins with preparatory work on various water-soluble ligands (cf. Table 1). 

Following the recommendations of Manassen [18] the history of biphasic hydroformylation began with work on various water-soluble ligands (Table 1). After this preparatory work on various aspects [30], Kuntz [22, 199] expressed the basic idea of a new generation of water-soluble oxo catalysts with triphenyl-phosphine trisulfonate (TPPT S, as the Na salt, as compared with TPPMS and TPPDS, the mono- and disulfonate) as ligands for a Rh-based oxo process, mainly for the hydroformylation of lower olefins such as propene (eq. (5)). 

Influence of chain length and spacer length on Tg, on the heat capacity increment at Tg (ACp), and the shape of the Cp(T) curve win be presented in the first paper (preliminary results can be found in (3)). Subsequently, we will address influence of thermal history in the isotropic phase and N+I biphase, physical aging below Tg and Tg in blends of LCPs. Finally, an interpretation of the macroscopic data in terms of molecular organization in these and other nematic LCP glasses will be attempted. 

The history of biphasic homogeneous catalysis starts with Manasserfs statement... 

Fig. 1. The Nematic-Isotropic Biphase. Nematic fraction fjj measured by NMR on slow cooling from the isotropic phase (sample thermal history as in ref. 5). Comparison with jTxN IN be DSC peak width and Tc-T2 or biphase observed by microscopy (scanning rate 10 C/min. thermal history as in ref. 5). Sample DDA-9 Mn=4,000.

This chapter contains the following sections Brief overview of rigid-flexible (RF) polymers Supercooling at the isotropic-mesophase transition Memory of thermal history in the isotropic phase and Memory of thermal history in the nematic-isotropic biphase and aging of the mesophase. 

The N + I biphase finds its origin in polydispersity in chain length coupled with polydispersity in chain flexibility and is observed within a temperature range delineated by and T. Polarizing microscopy observation of the biphase in Pi (n = 10, M = 18 700) is illustrated in Figures 6.5a-c for three different conditions of thermal history [42]. It is apparent that textures and biphase width both depend on sample thermal treatment. 

Small isotropic droplets, c, 1 im or smaller in size, are not easily resolved by microscopy. A minor isotropic component is often found to trail at the lower temperature range within the biphase and its presence can be overlooked [25]. Yet a finely dispersed I phase can be expected to influence rheological behavior, order and orientation dynamics in the mesophase, as well as the mechanical properties of the resulting solid phase. In contrast to microscopy or DSC which detect macroscopic behavior, NMR provides a molecular or segment level view of morphology and cannot distinguish between phase and microphase separation. Thus accurate biphase delineation may be delicate to accomplish. We should further note that the customary dynamic scans do not provide the equilibrium value of biphase width but rather an apparent value as determined by thermal history (section 6.5). 

Although the I phase is devoid of long range order, it is characterized by a metastable morphology which is determined by the thermal history and structure of chains. Memory of this morphology is reflected in the biphase, mesophase and solid state achieved on cooling from the I precursor. The following examples illustrate such memory effects. 

Because of its processing history, DURASUL has a biphasic crystalline microstructure that is manifested in two distinct thermal transitions during a... 

Fig. 5.108 An example of the biphasic structure of X7G formed by specific thermal history is shown by TEM. An ultrathin, longitudinal section of the fiber is shown to have dense elongated dispersed phase particles present in a fibrillar matrix. Microdiffraction of the dispersed phase shows it is amorphous (inset 1) and likely PET, and a pattern for the matrix (inset 2) appears oriented and is likely the PHBA.

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